I have just spoken to a big towbar supplier. Apparently it can be done, and behind the bumper is a ready to use attachment point. One has to cut a hole in the bumper, and maybe have a plastic clip-in cover to fill the hole if the towbar is removable. The towbar kit comes with a replacement crush bar (the bit of steel which sits behind the plastic rear bumper) which is much thicker than the original crush bar.
But the biggest supplier, Westphalia, doesn't [yet] list a model for the current Scirocco.
The hard bit is the electrics. The Canbus system means one cannot parallel-wire the trailer lights, like in a "normal" car (and if you did, duff bulb detection would stop working). In fact one cannot even get to the terminals of the bulbs, without a mess. There are two solutions: (1) a Canbus module, about £200, which then drives the trailer bits, or (2) a relay module, slightly less than £200, which measures the current drawn by each light cluster, and determines which of the lights within it are activated, and then switches on the correct trailer lights.
The latest Golf has the same issues, apparently, and a towbar is best part of £400.
I was also told that if you have a towbar attachment, even the foglamp has to be duplicated and this is tested on the MOT even if the towbar is not present on the MOT, and they check all the lights to the trailer work correctly. But if the removable towbar also involves an inline connector of some sort (so the normal 13-pin trailer connector is gone altogether) they cannot test anything

I am after a towbar for a very lightweight trailer, not a caravan or anything like that.